Noise can be a persistent concern for electronic devices because the noise can come from a variety of sources (both internal and external) and can adversely affect the devices' desired signals. In some circumstances, the noise can be related to the power adapters used to power the electronic devices.
FIGS. 1A and 1B illustrate two types of power adapters that are typically used to power electronic devices. In the example of FIG. 1A, “Type B” power adapter 110 can include plug 112 to plug into a power source, e.g., a wall outlet, to receive a voltage, e.g., AC voltage. The plug 112 can have three prongs, including live voltage prong 112-a, neutral prong 112-b, and ground prong 112-c. The adapter 110 can also include connector 113 to connect to an electronic device to send a voltage, e.g., DC voltage, to power the device. The adapter 110 can further include power circuit 111 to receive the voltage from the power source via the plug 112, transform the received voltage into a voltage that is compatible with the connected device, and send the compatible voltage to the device via the connector 113. In the example of FIG. 1B, “Type A” power adapter 120 can be the same as the Type B adapter 110, except Type A adapter plug 122 has two prongs rather than three. The two prongs of the plug 122 can include live voltage prong 122-a and neutral prong 122-b. The Type A adapter's power circuit 121 can receive voltage from a power source via the plug 122, transform the received voltage into a voltage compatible with a connected electronic device, and send the compatible voltage to the device via connector 123 to power the device.
As the Type B adapter 110 has ground prong 112-c that can couple to earth ground, noise induced in the adapter can be shunted to ground rather than into components of a connected electronic device. On the other hand, the Type A adapter 120 does not have a ground prong and therefore can induce noise that can be introduced into the connected electronic device that the adapter powers.
Because many electronic devices use the Type A adapter, the challenge is to suppress induced noise in those devices while using that adapter.